Sorry, this will only work on short focal flange mounts, which basically means mirrorless. So, there might be an EF-to-EFM version, but never an EFS-to-EF version.

One more reason to support my belief that mirrorless is the future.

Why does it require a short flange mount? A telecompressor is like an inverse teleconverter.

An optic free adapter such as an EOS to NEX, F to EOS, or M to X-mount all require the adapter to be of a precise depth to bridge the gap between the two flange depths, placing the lens at the correct distance to maintain the usual focus range.

However, optics placed between the body and lens such as teleconverters and the Canon FD to EOS adapter overcome this limitation. As long as its got the correct distance from the lens to the telecompressor, and the rear of the telecompressor is able to project it's image correctly from its rear element to the sensor, all is good.

Sorry, this will only work on short focal flange mounts, which basically means mirrorless. So, there might be an EF-to-EFM version, but never an EFS-to-EF version.

One more reason to support my belief that mirrorless is the future.

This particular adapter is designed for the flange mount on a micro 4/3, but it could be designed for any flange length. However, it requires a larger format lens in order to eliminate viginetting, so to use it on FF, you would need at least a medium format lens. Since MF lenses have a long flange length, the same principle would work.Don't expect to see one for FF, probably not for APS-C either, there are just not enough people with MF lenses laying around to make it economically practical.

pharp

I'd be interested to see if this works with 3rd party cropped body lenses on a M4/3. The Sigma 8-16 (uses the EF mount, even though designed for APS-C bodies) is quite sharp and might be alot of fun. I'm assuming they'd vignette on the NEX.

ok, so in theory you could make one that allows you to use EF lenses on your EF-S camera without losing FoV

but definitely not with this design: this adapter is actually shorter than a dumb glass-less one

I would think* there must be pretty big downsides to having an actually longer adapter (which is what you need for that EF to EF-S thing) while mantaining infinite focus, plus there's a mirror so you can't end up close to the sensor... I'd pretty much rule it out

* that guess is based on the fact that they had no restritions regarding size, and they ended up with a shorter-than-usual adapter: this must be what gives you the best IQ